The mediastinum is the space within the thorax between the lungs, containing the heart, major blood vessels, esophagus and other structures. It is divided into superior and inferior mediastinum. The superior mediastinum contains the thymus gland, great vessels of the neck, trachea and esophagus. The inferior mediastinum is further divided into anterior, middle and posterior mediastinum by the pericardium. The middle mediastinum contains the heart and pericardium, while the posterior mediastinum contains the descending aorta and esophagus. Infections of the neck can spread into the mediastinum through fascial planes. Tumors can compress mediastinal structures

1. MEDIASTINUM
BY:
PHANINDRA PRASAD POUDEL
ASSISTANT PROFESSOR
DEPARTMENT OF ANATOMY

2. DEFINATION
• Space between rt & lt
lungs & pleural sacs
• Extension:
Thoracic inlet above
to diaphragm below
Sternum anteriorly to
thoracic vertebrae
behind

3. BOUNDARIES
• Anteriorly: posterior
surface of sternum
• Posteriorly: anterior
surface of bodies of 12
thoracic vertebrae,
intervertebral disc,
anterior longitudinal
ligament
• Superior: thoracic inlet
• Inferior: upper surface of
diaphragm
• On each side: mediastinal
pleura of lungs

4. DIVISION
• Divided into superior
& inferior
mediastinum by an
imaginary plane
passing through the
sternal angle
(manubriosternal
joint) to the lower
border of 4th thoracic
vertebra.

5. SUPERIOR MEDIASTINUM
BOUNDARIES:
 Anterior: posterior surface of
manubrium sterni
 Posterior: anterior surface of
bodies of T1-T4 vertebrae,
intervertebral disc, anterior
longitudinal ligament
 Superior: thoracic inlet
 Inferior: horizontal plane
extending from sternal angle
(manubriosternal joint) to the
lower border of T4
 On each side: mediastinal
pleura and lungs

6. CONTENTS
• Arranged into 3 groups
a. Retrosternal:
 Origin of
sternothyroid &
sternohyoid
muscles
 Thymus gland
 Rt & lt
brachiocephalic
veins, Superior
vena cava, Left
superior
intercostal vein

7. CONTENTS…
b. Intermediate
structures:
Arch of aorta with
its 3 large
branches;
brachiocephalic
trunk, left common
carotid & left
subclavian arteries
Phrenic nerves,
vagus nerves &
cardiac nerves

8. CONTENTS…
c. Prevertebral
structures:
 Trachea with
paratracheal &
tracheosophageal
lymph nodes
 Esophagus
 Left recurrent
laryngeal nerve
 Thoracic duct
 Origin of longus colli
from T3

9. CLINICAL ANATOMY:
• Prevertebral fascia of neck:
 Extends into superior mediastinum & attached to T4
 Infection in neck may extend into superior mediastinum
• Pretracheal fascia of neck:
 Extends upto superior mediastinum & attached to the
tunica adventitia of arch of aorta
 Infection in between the pretracheal & prevertebral
fascia extends into superior mediastinum
 Results into infection in the superior mediastinum,
mediastinitis

10. II CLASS

11. INFERIOR MEDIASTINUM
BOUNDARIES:
 Anterior: posterior surface of
the body of sternum
 Posterior: anterior surface of
the bodies of T4-T12
vertebrae, intervertebral disc,
anterior longitudinal ligament
 Superior: horizontal plane
extending from sternal angle
(manubriosternal joint) to the
lower border of T4
 Inferior: diaphragm
 On each side: mediastinal
pleura and lungs

12. DIVISION OF THE INFERIOR MEDIASTINUM
INFERIOR MEDIASTINUM:
Divided by
pericardium into:
Anterior
mediastinum
Middle mediastinum
Posterior
mediastinum

13. ANTERIOR MEDIASTINUM
BOUNDARIES:
 Anterior : posterior
surface of body of
sternum
 Posterior : fibrous
pericardium
 Superior : transthoracic
plane
 Inferior : diaphragm
 On each side :
mediastinal pleura and
lungs

14. CONTENTS OF ANTERIOR
MEDIASTINUM
• Superior & inferior
sternopericardial
ligaments
• Loose aerolar
tissue
• Retrosternal lymph
nodes
• Mediastinal
branches of
internal thoracic
artery

15. MIDDLE MEDIASTINUM
BOUNDARIES:
Widest
subdivision
Occupies within
the fibrous
pericardium
Bounded on
each side by
mediastinal
pleura and lungs

16. CONTENTS OF MIDDLE MEDIASTINUM
 Pericardium enclosing heart
 Ascending aorta
 Pulmonary trunk with its rt &
lt branches
 Four pulmonary veins
 Lower half of SVC
 Arch of azygos vein
 Bifurcation of trachea- rt & lt
bronchi
 Deep cardiac plexus,
phrenic nerves,
pericardiophrenic vessels,
inferior tracheobronchial
lymph nodes

17. POSTERIOR MEDIASTINUM
BOUNDARIES:
 Anterior : above
downwards
 Bifurcation of trachea
 Pulmonary vessels
 Fibrous pericardium
 Posterior sloping surface of
diaphragm
 Posterior : bodies of
lower 8 thoracic
vertebrae, intervertebral
discs, anterior
longitudinal ligament

18. POSTERIOR MEDIASTINUM
Superior :
imaginary
horizontal plane
Inferior :
diaphragm
On each side :
mediastinal
pleura and lungs

19. CONTENTS OF POSTERIOR MEDIASTINUM
 Oesophagus
 Descending aorta &
its branches
 Azygos, hemiazygos
& accessory
hemiazygos veins
 Thoracic duct
 Vagus nerves,
splanchnic nerves
 Posterior mediastinal
lymph nodes

20. CLINICAL ANATOMY
a. Connection of posterior mediastinum with the
spaces around the neck via superior mediastinum
o Connection with retropharyngeal space, space
between trachea & esophagus, spaces around carotid
sheath of neck
o Infections of neck may gravitate into superior &
posterior mediastinum

21. b. Compression of mediastinal structures by
any form of tumours results into mediastinal
syndrome with various symptoms:
i. Obstruction of superior venacava gives rise to
engorgement of veins of upper half of the body
ii. Pressure over the trachea causes dyspnea &
cough
iii. Pressure over the esophagus causes dysphagia

22. iv. Pressure over the left recurrent laryngeal nerve
causes hoarseness of voice
v. Pressure over the intercostal nerve results into
intercostal neuralgia
vi. Pressure over the vertebral column causes the erosion
of vertebral bodies
vii. Pressure over the phrenic nerve causes the paralysis
of diaphragm

23. HOME ASSIGNMENT
1. Draw a well labeled diagram showing
the subdivisions of Mediastinum.
2. What are the boundaries and contents
of Inferior mediastinum?
THE END